Conventionally, a hollow fiber membrane module has been used for a lot of purposes such as manufacturing an axenic water, drinking water, and highly pure water, and cleaning an atmosphere. In addition to these purposes, in recent years, the hollow fiber membrane module is used for other purpose for processing a highly contaminated water in secondary processing and a third processing in a sewage plant, a solid-liquid separation in a waste water treatment tank, and a solid-liquid separation of a suspended solid (hereinafter called SS) in an industrial waste water.
A hollow fiber membrane module which is preferably used for filtering a highly contaminated water is disclosed in documents such as Japanese Unexamined Patent Applications, First Publication No. Hei 5-261253, No. H6-000342, and No. H6-000340. According to such a hollow fiber membrane module, an end section of a sheet hollow fiber membrane bundle is contained and fixed in side a rectangular housing by a fixing resin. These hollow fiber membrane module is manufactured by pouring the fixing resin in the housing, fixing the end section of the hollow fiber membrane bundle on the housing by the fixing resin, and cutting a part of the fixing resin such that the end section of the hollow fiber membrane is opened.
However, in such a method, it is necessary to use a housing having a large diameter because it is necessary to insert a cutter in the housing. Therefore, there is a problem in that an integration of the hollow fiber membrane module per a unit volume is low in a hollow fiber membrane module unit when a plurality of the hollow fiber membrane modules are integrated so as to assemble the hollow fiber membrane module unit.
For solving the above problem, a hollow fiber membrane module which is disclosed in the Japanese Unexamined Patent Application, First Publication No. Hei 10-57775 can be named. This hollow fiber membrane module is manufactured by forming a slit on the housing unit which is made from a commercial pipe, forming a potting weir section around the slit, inserting the hollow fiber membrane bundle in which an end section of the hollow fiber membrane is opened in advance in the slit section, pouring a fixing resin inside of the resin potting weir section such that an end section of the hollow fiber membrane is not closed; and fixing the hollow fiber membrane bundle by the fixing resin.
In the manufacturing method of the above hollow fiber membrane module, the hollow fiber membrane bundle is fixed on the housing by the fixing resin, and after that, a process for cutting a part of the fixing resin such that an end section of the hollow fiber membrane is open is omitted. By doing this, it is possible to make a diameter in the housing smaller.
Also, in Japanese Unexamined Patent Application, First Publication No. 200-84373, a hollow fiber membrane module is proposed which is realized by modifying a hollow fiber membrane module which is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 10-57775. FIG. 27 is a perspective view for such a hollow fiber membrane module. FIG. 28 is a cross section in the housing in the hollow fiber membrane module shown in FIG. 27.
The hollow fiber membrane module 11 approximately comprises a pair of housings 12, a hollow fiber membrane bundle 14 in which a plurality of hollow fiber membranes 13 are bundled as a sheet, and end cap 17 which is attached to and end of the housing 12 and has a processed water exit 16, and an end cap 18 which is attached to another end of the housing 12 and does not have a processed water exit. The hollow fiber membrane bundle 14 is fixed on the housing by the fixing resin 15 under condition that the hollow fiber membrane bundle 14 is inserted in the housing 12 and the opening end section 19 in the hollow fiber membrane 13 is maintained open.
The housing 12 is a hollow columnar member having a U-letter shape which is provided with a hollow inner path 21 which is formed in the housing 12, a slit opening section 22 which is formed on a surface of the housing 12, weirs 24 which are disposed unitarily with the housing unit 23 on both sides of the opening section 22 in parallel with the opening section 22, and a resin pouring section 25 which is sandwiched by the weirs 24.
In the hollow fiber membrane module 11, a diameter in the housing 12 can be further smaller by adapting a housing 12 having a cross section in U-letter shape; thus, it is possible to increase the integration. Simultaneously, an anti-pressure characteristics in the housing 12 improves. A water pressure caused in a reverse-cleaning is applied to the housing 12 repeatedly when a reverse cleaning operation is performed on a solid member in a highly contaminated water which adheres on an outer surface of the hollow fiber membrane 13; therefore, it is necessary to realize an anti-pressure characteristics in the housing 12 particularly when such a highly contaminated water is filtrated.
When a highly contaminated water is filtrated by using such a hollow fiber membrane module 11, a method in which an air bubbling operation by using an air dispersing tube can be commonly used for cleaning a solid member in the highly contaminated water which adheres on an outer surface of the hollow fiber membrane 13 in addition to the above reverse-cleaning method. In this way, various stresses are generated in the hollow fiber membrane module 11 when a filtrating operation is performed by using the hollow fiber membrane module unit. In particular, an ascending flow which is generated in the air bubbling operation applies an upward force on the hollow fiber membrane 13; thus, a force toward the hollow fiber membrane is applied on the housing 12 such that the housing 12 is pulled by the hollow fiber membrane 13 which is driven by the ascending flow. In this way, a deflection in the housing 12 which is caused by the stress which is generated by the air bubble becomes a reason for damaging the hollow fiber membrane 13.
Also, there is a sag in the hollow fiber membrane bundle 14 caused by the deflection in the housing. As a result of this, it sometimes occurs that the hollow fiber membrane bundles 14 in the neighboring hollow fiber membrane modules 11 are entangled each other in the hollow fiber membrane module unit. Also, there are problems in that the hollow fiber membrane module 11 is broken, crumbs and a hair contained in the highly contaminated water accumulates, and a uniform air bubbling operation is not realized because of such an entanglement of the hollow fiber membrane bundle 14 when the hollow fiber membrane module unit is used for a long time.
As explained above, performance in the hollow fiber membrane module unit which uses the hollow fiber membrane module 11 and the module depends on the deflection in the housing 12.
For such a deflection in the housing which is explained here, it is possible to name deflections in two directions mainly such as a deflection in a longitudinal direction of the hollow fiber membrane bundle which is generated during a filtrating operation of the hollow fiber membrane module unit and a deflection in a direction orthogonal to the longitudinal direction of the hollow fiber membrane bundle. It is possible to prevent a deflection in a direction orthogonal to the longitudinal direction of the hollow fiber membrane bundle by various methods such as a method in which dimension of the housing which is used for the hollow fiber membrane module is designed in advance such that the housings are disposed tightly when the hollow fiber membrane module is assembled to be a unit, a method in which a spacer or the like is inserted in a space between the housings in the hollow fiber membrane module when the hollow fiber membrane module is assembled to be a unit, or other simple method. However, a method in which a deflection in the housing in the longitudinal direction of the hollow fiber membrane bundle is restricted so as to prevent the entanglement of the hollow fiber membrane has not been proposed specifically.
Also, in such a hollow fiber membrane module 11, it is necessary to attach end caps 18, 18 for sealing an end section of the housing 13 on the housing 13 in a water-tight manner so as to collect a processed water.
The end caps 17, 18 are usually attached to the housing before the fixing resin 15 is poured into the resin pouring section 25 in the housing 12. For attaching the end caps 17, 18 to the housing 13, a solvent bonding agent, or a bonding resin which is equivalent to the fixing resin 15 are used under condition that members for the end cap 17, 18 and the housing 12 are a polycarbonate member, an acrylic resin member, an ABS resin (acrylonitrile-butadiene-styrene resin) member or a polyvinyl chloride member. These bonding agent is applied to an area in which the housing 12 and the end caps 17, 18 contact each other, after that, the housing 12 and the end caps 17, 18 are attached together.
However, in the hollow fiber membrane module 11 which is explained above, there is a case in which an area to which a bonding agent is applied is broken when an external press is applied to the housing 12, that is, when an excessive force is applied to the end caps 17, 18 which are attached together with the housing 12 repeatedly. Also, it is not easy to apply the bonding agent to the end caps 17, 18; therefore, there is a problem in that a production efficiency decreases.
Furthermore, in the housing which is explained above, there is an non-uniformity in the dimensions in the weir section 24 which is formed on an outer surface of the housing unit 23 and the resin pouring section 25 which is surrounded by the weir section 24 according to the molding condition of the housing 12. In some cases, there is a case in which the weir section 24 is inclined toward thereinside. Also, there is a case in which the hollow fiber membrane 13 falls because of inaccuracy in the dimension of the opening section 22 and the hollow fiber membrane 13 when the hollow fiber membrane 13 is inserted in the housing 12 and the hollow fiber membrane 13 is sandwiched in the opening section 22 so as to be fixed there. In such cases, it is not possible to obtain a sufficient capacity in the pouring section 25. Also, there is a case in which the fixing resin 15 leaks out of the housing 12 when the fixing resin 15 is poured into the resin pouring section 25. Furthermore, sufficient amount of the resin is not used in a potting operation; thus, the fixing resin 15 does not prevail entirely; therefore, a product has a defect. Also, there is a concern for an anti-pressure characteristics and durability because of insufficiency of the potting resin.
Therefore, a main object of the present invention is to provide a hollow fiber membrane module having a superior durability in which the hollow fiber membrane and the housing are not damaged and a method for manufacturing the same.
More specifically, an object of the present invention is to provide a hollow fiber membrane module in which it is possible to increase the integration of the hollow fiber membrane module per a unit volume of the hollow fiber membrane module unit and has a less deflection in the housing caused by factors such as an air bubble and less entanglement of the hollow fiber membrane, and a hollow fiber membrane module unit using the same.
Also, other object of the present invention is to provide a hollow fiber membrane module having a superior mechanical tightness in a section in which the housing and the end caps are attached together, and a method for manufacturing such a hollow fiber membrane module easily and efficiently.
Also, other object of the present invention is to provide a housing in which it is possible to pour the resin and increase a volume for pouring the resin thereinto so as to fix the hollow fiber membrane by the resin while improving an anti-pressure characteristics, and a hollow fiber membrane module using the same.